1. Field of the Invention
This invention relates to a pole for use in delineating boundaries, such as a slalom pole marking boundaries along a ski slope and, in particular, to a pole constructed to facilitate a bending of its upper portion upon impact due to a moving object, for example, striking of the pole by a down-hill skier. The instant pole is so constructed as to minimize any injuries to the skier or damages to the pole.
2. Description of the Prior Art
Generally, slalom poles are known in the prior art.
One such structure is shown in U.S. Pat. No. 3,279,133 to De Korte. De Korte discloses a boundary marker; the upper part of it is adapted to return to the vertical position after being struck by a moving object. This device comprises hollow upper and lower pole sections which are joined by means of an external spring threaded onto both the upper and lower sections. When the pole is struck, the spring is flexed, allowing the upper pole to pivot at ground level and return to the vertical. A drawback of this device is that the spring itself bends and thus is liable to become distorted upon continued use. Furthermore, at ground level the spring is external to the device and susceptible to corrosion and impairment to function due to clogging from such substances as dirt and ice.
The device disclosed in U.S. Pat. No. 4,270,873 to Laehy et al. overcomes many of the disadvantages of the patent to De Korte by housing the spring within the pole. This eliminates the exposure of the spring to damaging elements. The patent to Laehy, however, suffers from the drawback that if the pole is bent more than 90.degree. there are no means for ensuring that the spring coils are urged together so as to resurrect the pole to a vertical position. This would therefore require to adjust the pole manually after each collision with attendant delays and therefore make it impractical for use in such events as slalom races. Furthermore, as snow can accumulate in the lower tubes of the pole, this may cause icing up and breaking of the spring. Another disadvantage of the patent to Laehy is that no anchoring means is provided at the bottom end of the pole to ensure that the pole be firmly secured in either ice or in deep light snow, which are typical environments in slalom races.
Reference is also made to the U.S. Pat. No. 1,726,817 to Franklin and the U.S. Pat. No. 2,050,579 to Murray. Both relate to traffic signals. Both of these patents have a solid pole, the bottom portion of which is inserted in a resilient tube. The major drawback of this type of structure is that the upper portions of the pole can be broken off upon impact.
U.S. Pat. No. 3,698,144 to Stratton relates to a detachable post anchor for use with highway marker posts. This construction has no resilient means for returning the pole to the original position upon impact, and the anchor includes a spike which is to be driven into the ground and therefore requires a great deal of effort in securing it onto an icy surface.
Reference is made to U.S. Pat. No. 2,286,959 to Haines which relates to a Highway Traffic Post.
Reference is lastly made to U.S. Pat. No. 4,073,254 to Marker which relates to a sailing mast for sailing boards having a flexible portion at the bottom of the mast for bending. A major drawback of this structure is that it uses a sprung rope to resist the bending of the mast, and is, of course, bare of any anchoring in snow or ice.